1. Field of the Invention
The present invention relates to a lens barrel, used in an optical system for an optical device such as a camera, for changing its power and adjusting its focus.
2. Related Background Art
Conventionally known as a lens barrel, used in an optical system of an optical device such as a camera, for changing its power and adjusting its focus is one having four lens groups, all of which are attached to a frame expandable from the camera body, whereas the lens groups are appropriately moved in the optical axis direction by use of a cam mechanism so as to change the power and adjust the focus, as disclosed in Japanese Patent Application Laid-Open No. HEI 7-20369.
This lens barrel comprises a barrier blade, disposed in front of a taking optical system, for opening/closing an optical path; a lens driving mechanism for advancing/retracting a part of the taking optical system upon a focusing operation of the taking optical system; a barrier driving mechanism for opening/closing the barrier blade; a first transmission mechanism for transmitting a driving force of a driving source to the lens driving mechanism; and a second transmission mechanism for transmitting the driving force of the driving source to the barrier driving mechanism, in which the transmission of the driving force to the second transmission mechanism is switched via a clutch mechanism as appropriate. The switching of the clutch mechanism is carried out by utilizing a pivotal member, so as to enhance the space efficiency, thereby reducing the size of the camera.
If the driving source is driven in such a lens barrel in the state where the driving force is transmitted to the barrier driving mechanism, the barrier will be opened/closed, whereby no lens movement of the taking optical system can be carried out as a focusing operation. Consequently, for taking a photograph, it is necessary to attain a state where the lens barrel is expanded and so forth, so that no driving force is transmitted to the barrier driving mechanism.
Hence, the expanding of the lens barrel narrowly restricts the power-varying range of the taking optical system. For widening the power-varying range, it is desirable that a photographing preparation state be attained without expanding the lens barrel in the state where the barrier is open. In order to prevent shutter chances from missing, it is desirable that shutter release operations be carried out instantly without expanding the lens barrel in the state where the barrier is open.
In order to eliminate such a problem, it is an object of the present invention to provide a lens barrel which can carry out barrier opening/closing operations and lens moving operations of a lens optical system by use of a single driving source, and can adjust the focus without any obstruction even in a state allowing the barrier to open/close.
In order to achieve such an object, the present invention provides a lens barrel comprising a plurality of cylindrical bodies, accommodating a lens optical system having a plurality of lens groups, adapted to expand and collapse the lens optical system in a multistage manner; a driving source, installed in one of the cylindrical bodies, for generating a predetermined driving force; a first driving transmission mechanism for transmitting the driving force of the driving source to a barrier opening/closing mechanism; a second driving transmission mechanism for transmitting the driving force of the driving source to a moving mechanism of the lens optical system; and driving transmission switching means for placing the first driving transmission mechanism into a state capable of transmitting the driving force to the barrier opening/closing mechanism when the plurality of cylindrical bodies are collapsed to a predetermined extent or more, and placing the first driving transmission mechanism into a state incapable of transmitting the driving force to the barrier opening/closing mechanism when the plurality of cylindrical bodies are expanded to a predetermined extent or more; wherein the lens optical system is totally expanded so as to adjust a focus in a state where the driving source is stopped if the driving force is made transmittable to the barrier opening/closing mechanism by the driving transmission switching means.
The lens barrel in accordance with the present invention may be configured such that the first driving transmission mechanism has two gears adapted to switch between meshed and unmeshed states, the driving force is transmitted by way of the two gears, the driving transmission switching means causes the two gears to mesh with each other so as to place the first drive transmission mechanism into a state capable of transmitting the driving force when the plurality of cylindrical bodies are collapsed to a predetermined extent or more and causes the two gears to come out of mesh with each other so as to place the first driving transmission mechanism into a state incapable of transmitting the driving force when the plurality of cylindrical bodies are expanded to a predetermined extent or more.
The lens barrel in accordance with the present invention may be configured such that the driving transmission switching means comprises a rod adapted to move toward the two gears when the plurality of cylindrical bodies are collapsed to a predetermined extent or more; and a swing plate, in which one of the two gears is installed, adapted to swing so as to place the two gears in the unmeshed state when the rod is moved.
According to these aspects of the present invention, a single driving source can open/close the barrier and adjust the focus of the lens optical system. Also, if the lens optical system is totally expanded so as to adjust the focus in a state where the driving force is transmittable to the barrier opening/closing mechanism, the focus can be adjusted while the driving source is stopped. If the lens barrel is employed in a camera or the like, photographing will be possible without expanding the lens barrel. Therefore, the power-varying range of the taking optical system can be widened, which enables prompt photographing.
Also, the present invention provides a lens barrel comprising a plurality of cylindrical bodies, accommodating a lens optical system having a plurality of lens groups, adapted to expand and collapse the lens optical system in a multistage manner; a driving source, installed in one of the cylindrical bodies, for generating a predetermined driving force; a first driving transmission mechanism for transmitting the driving force of the driving source to a barrier opening/closing mechanism; a second driving transmission mechanism for transmitting the driving force of the driving source to a moving mechanism of the lens optical system; driving transmission switching means for placing the first driving transmission mechanism into a state capable of transmitting the driving force to the barrier opening/closing mechanism when the plurality of cylindrical bodies are collapsed to a predetermined extent or more, and placing the first driving transmission mechanism into a state incapable of transmitting the driving force to the barrier opening/closing mechanism when the plurality of cylindrical bodies are expanded to a predetermined extent or more; and switching error recovery means for expanding the plurality of cylindrical bodies to a predetermined position if the driving transmission switching means is not in a state capable of transmitting the driving force to the driving transmission switching means when the plurality of cylindrical bodies are collapsed to a predetermined extent or more, and then collapsing the plurality of cylindrical bodies to a predetermined position.
The lens barrel in accordance with the present invention may be configured such that the first driving transmission mechanism has two gears adapted to switch between meshed and unmeshed states, the driving force is transmitted by way of the two gears, the driving transmission switching means causes the two gears to mesh with each other so as to place the first drive transmission mechanism into a state capable of transmitting the driving force when the plurality of cylindrical bodies are collapsed to a predetermined extent or more and causes the two gears to come out of mesh with each other so as to place the first driving transmission mechanism into a state incapable of transmitting the driving force when the plurality of cylindrical bodies are expanded to a predetermined extent or more, and the switching error recovery means expands the plurality of cylindrical bodies to a predetermined position if the two gears are not in a normal meshed state when the plurality of cylindrical bodies are collapsed to a certain extent or more, rotates at least one of the two gears, and then collapses the plurality of cylindrical bodies to a predetermined position.
According to these aspects of the present invention, if the first driving transmission mechanism fails to attain a state capable of normally transmitting the driving force to the barrier opening/closing mechanism when collapsing the lens barrel, the lens barrel may be collapsed again after being expanded, whereby the driving force transmitting state of the first driving transmission mechanism can be recovered. Also, if the lens barrel is expanded to a predetermined position, at least one of the two gears is rotated, and then the lens barrel is collapsed to a predetermined position, the two gears can favorably be meshed with each other. Since the driving force transmitting state of the first driving transmission mechanism is recovered, it is not required to be processed as an error. Therefore, camera failures can be reduced.
Also, the present invention provides a lens barrel comprising a plurality of cylindrical bodies, accommodating a lens optical system having a plurality of lens groups, adapted to expand and collapse the lens optical system in a multistage manner; a driving source, installed in one of the cylindrical bodies, for generating a predetermined driving force; a first driving transmission mechanism for transmitting the driving force of the driving source to a barrier opening/closing mechanism; a second driving transmission mechanism for transmitting the driving force of the driving source to a moving mechanism of the lens optical system; driving transmission switching means for placing the first driving transmission mechanism into a state capable of transmitting the driving force to the barrier opening/closing mechanism when the plurality of cylindrical bodies are collapsed to a predetermined extent or more, and placing the first driving transmission mechanism into a state incapable of transmitting the driving force to the barrier opening/closing mechanism when the plurality of cylindrical bodies are expanded to a predetermined extent or more; and drive control means for driving and controlling the driving source, the drive control means setting a lower driving speed for the driving source and driving the driving source when the first driving transmission mechanism is placed in a state capable of transmitting the driving force to the barrier opening/closing mechanism.
According to this aspect of the present invention, the driving speed of the driving source is set lower when the first driving transmission mechanism is placed in a state capable of transmitting the driving force to the barrier opening/closing mechanism due to the meshing of gears and the like, whereby the meshing sound of the gears for transmitting the driving force can be lowered.